Semiconductor fabrication methods regularly utilize various types of etching processes. One type of etching process is a dry etching process. A dry etching process uses bombardment of ions from reactive gases to remove material from exposed surfaces. Another type of etching process is a wet etching process. A wet etching process uses a chemical solution to remove exposed material.
Another process regularly used in semiconductor fabrication methods is a doping process. The doping process involves injecting dopants into a semiconductor material to change the electrical properties of the semiconductor material. One way to perform a doping process is to deposit a thin layer of doping oxide onto the substrate. The doping oxide includes the desired type of dopants. Then, an annealing process is performed that causes the dopants of the doping oxide layer to diffuse into the substrate. Thus. The doping oxide layer acts as a solid diffusion source.
The doping oxide layer is typically patterned so that only the appropriate regions of the underlying substrate are doped. Patterning the doping oxide layer involves use of a patterning layer, such as a photoresist layer, and an etching process to remove exposed portions of the doping oxide layer. Using a dry etching process can damage the underlying substrate. Using a wet etching process can cause lateral etching of the doping oxide layer beyond the sidewalls of the patterning layer.